This invention relates to sealing apparatus for use in rotary machinery for preventing a working substance under pressure from leaking about a shaft of the machine.
More specifically, this invention relates to an improvement on ISO-SEAL structure as conventionally utilized in relation to high speed rotating shafts. In this particular arrangement, an annular rotating element or collar is affixed to the shaft and coacts with a non-rotating sleeve through means of a free floating carbon ring, interposed therebetween, to prevent working fluids from leaking about the shaft into the surrounding areas of lower pressure. The sleeve of the sealing assembly is yieldably urged against the free floating carbon ring so as to bias the ring in face to face contact against the rotating member. In prior art devices the outside of the assembly is flooded with oil to provide the necessary cooling.
In practice, oil or other lubricant has been pumped under pressure to flood the free floating carbon ring. The oil is then directed in two directions along a shaft, one being towards the high pressure area such that oil contaminated with the working fluid is collected at the contaminated oil discharge and the other being away from the high pressure area to a separate clean oil collection area. In order to prevent high pressure oil from being discharged out of the seal a separate breakdown bushing and seal is provided on the shaft downstream from the rotating element to reduce oil flow along the shaft and to prevent oil that does travel along the shaft from being discharged at high pressure. A clean oil discharge area is provided to remove the oil from the seal assembly prior to passing through the breakdown bushing. The flow resistance created by the breakdown seal is sufficient to effect a pressure drop to atmospheric pressure in the oil flowing therethrough.
The present invention is an improvement on the above-described ISO-SEAL structure. The utilization of the breakdown bushing serves to increase the length of the seal since the breakdown bushing must be axially mounted downstream from the seal prior to the bearing supporting the shaft. If the breakdown bushing is removed the length of the shaft may be decreased. The removal of the breakdown bushing from the seal assembly further serves to reduce the number of components which may fail under operation. Hence, by the removal of this device the integrity and life of the entire seal may be improved.
The herein invention is directed at supplying lubricant directly to passageways in the free floating carbon ring. By directing the lubricant through the passageways the lubricant is decreased in pressure to essentially atmospheric pressure and thereafter flows downstream to a region of atmospheric pressure from which it is collected. The lubricant does not flow through a subsequent breakdown bushing. The reduction in pressure of the lubricant occurs in the passageways in the free floating ring or the contact seal sleeve obviating the necessity of maintaining a high pressure oil discharge area and a subsequent breakdown bushing. Additionally, by directing the oil directly through passageways in the sealing ring additional cooling of the sealing ring is provided allowing for performance at higher speeds and prolonging the life of the floating ring.
Additionally, disclosed is a combination which allows the high pressure working fluid to be supplied to both sides of the sealing ring to provide equalized forces for maintaining the carbon ring in the desired position. Also disclosed is the utilization of a carbon ring seal using both the interior and exterior surfaces of the carbon ring as tight fitting positioning surfaces eliminating the necessity of providing a metal band about the exterior of the carbon ring for supporting the ring further serving to secure the integrity of the entire seal arrangement.